Screen shot of led in a MacOS Terminal window about to pipe some data thru a Unix tool.
led is based mainly on three editors (in order of importance): IBM's PE2 (for PCs - a great editor), XMS's editor, and (could it be otherwise) IBM's XEDIT. It borrows very little from vi (the yank buffer is temporary pending PE2-style marks which never happened).
That was started in 1989. It didn't take long before the new editor could edit itself. The rest is history: led has never stopped growing (eg. around 2000, with a port to Windows over the Win32 API).
Except for the Windows version (where it manages its own window) it works only within VT100 terminals and emulations thereof (in particular xterms, MacOS Terminal -- but not most MS telnets). It also ran on DVIX M4020 terminals, but that's pretty irrelevant now.
It uses the VT100 keypad (for general functions) and c-keys (for editing). It has no regular-expression searching, no user-definable keys (although emulators might help here), and processes tabs and RETURNs in an unusual way. On xterm, it will be necessary to provide the keypad mappings. Beta release was summer '89 and it is has evolved ever since as needs dictated.
At its hottest, the WWLUG (world-wide led users group) had as many as 10 members!
Basic philosophy: unconstrained (move cursor anywhere, no jagged cursor moves), and WYSIWYG (strips trailing blanks for example).
Of all its features, I think the most important (as I discovered when I ported led to Windows) is system access from within the editor. It allows to extend the editor as much as desired with the tools of the system. This goes hand-in-hand with the Unix toolbox approach. For example, one can prepare batch files and submit them directly to the shell, pipe command output into the editor (eg. $ ls -lt | led), compare the file in the editor with the current version on disk, do finds, greps, directory lists and manipulate them. On Windows, this works best with a Cygnus (Unix-like) environment.
led is also the only editor I know of that can (in both its Unix, Windows, and the Mac versions) edit Unix, Mac and Windows text files, taking care not only of the different end-of-line conventions, but also of the ISO 8859-1 mappings!